U.S. Pat. No. 5,751,257, issued May 12, 1998 and U.S. Pat. No. 6,253,190 issued Jun. 26, 2001, both to Sutherland, show a system including a programmable shelf tag having a bistable liquid crystal display for displaying price data and a Universal Product Code (UPC) bar code, wherein the information programmed in the display remains on the display in the absence of power. The shelf tag has a set of synchronizing indicators and corresponding electrical contacts on the front side of the display. The shelf tag is constructed by forming patterned conductive character elements on top and bottom substrates and sandwiching a polymer stabilized liquid crystal between the patterned character elements.
The shelf tag disclosed by Sutherland is programmable with a hand held device that is in communication with a central computer that contains inventory and price information. The hand held device can be used to scan the synchronizing indicators to identify the location of the electrical contacts and supplies the electrical contacts with electrical signals to write appropriate information on the shelf tag. For inventory control and price updates, the hand held device is used to first read the UPC bar code on the shelf tag. If a price needs to be updated, the hand held device is then used to write the appropriate price information into the tag.
One problem with the system as described by Sutherland is that since each element of the display is written sequentially, a time is required to swipe the hand held device across the label. Another problem is the difficulty of maintaining consistent contact with the electrical contacts of the display as the hand held writing device is swept across the display.
There is a need therefore for an improved display tag writing device that avoids the problems noted above.